docs(admin-config-tool): commit spec docs and example configs

design.md, research.md (new), brief.md and requirements.md (updated
during spec authoring: Req 1.6 resolved/superseded by bundling, Req
5.5 added, Req 4.3/4.4 extended for limits.yaml) had been sitting
uncommitted since before implementation began -- the entire 18-task
implementation was built against these documents without them ever
landing in git.

src/configs/*.yaml + schema/*.schema.json: the example config
directory and bundled JSON schemas most of the test suite reads as
"real repo fixtures" (test_config_build.py, test_mapping.py,
test_validation.py, etc.) were likewise never committed -- those
tests would silently skip (skipif guards) rather than run for anyone
else checking out this branch.

src/configs/schema/scaler.schema.json

@@ -0,0 +1,28 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://example.com/schemas/scaler.schema.json",
+  "title": "Scalers",
+  "type": "object",
+  "additionalProperties": false,
+  "properties": {
+    "scalers": {
+      "type": "array",
+      "items": { "$ref": "#/$defs/Scaler" }
+    }
+  },
+  "required": ["scalers"],
+  "$defs": {
+    "Scaler": {
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "name": { "type": "string", "pattern": "^[A-Za-z0-9._-]+$" },
+        "type": { "type": "string", "description": "provider type, e.g. \"script\"" },
+        "conf_path": { "type": "string" },
+        "script_path": { "type": "string" },
+        "script_option": { "type": "string" }
+      },
+      "required": ["name", "type", "script_path"]
+    }
+  }
+}